(1) Field of the Invention
The present invention relates to the technical field of overlaying subtitles and graphics on stereoscopic video.
(2) Description of the Related Art
The above-mentioned overlaying technology (i) provides a playback apparatus with separate display planes for a video stream, subtitles, and graphics, (ii) overlays subtitles and graphics on each video frame in a high image quality video stream, and (iii) outputs the result to a device such as a connected display apparatus. This is a widespread form of technology for achieving highly realistic video.
It is predicted that, among display apparatuses connected to playback apparatuses, stereoscopic display apparatuses that allow viewers to enjoy not only flat video, but also video that seems to pop out of the screen, will grow in popularity in the near future. There are various methods used in stereoscopic display apparatuses, but a fundamental principle is a mechanism to show different pictures to the left eye and the right eye, using the parallax between eyes to create a pseudo-3D image.
For example, one often used method is to use shutter glasses. In this method, a viewer's right eye and left eye are alternately blocked at high speed by the glasses. By refreshing left-view images and right-view displayed by the display apparatus at high speed in sync with the operation of the glasses, it is possible for the glasses to make the left-view image shown by the display apparatus viewable only by the left eye, and conversely the right-view image viewable only by the right eye.
In order to show viewers a stereoscopic video at the same frame rate as an ordinary flat video, the display apparatus needs to have two times the ordinary response capability. For example, to show video with 60 frames per second, switching needs to be performed at 120 frames per second. Accordingly, the video stream to be shown needs to be encoded at 120 frames per second. One way of achieving a stereoscopic effect without increasing the frame rate is to encode a video stream with a side-by-side method as in Non-Patent Literature 1.
Another possibility is to use a checkered pattern as in Patent Literature 2.
Furthermore, technology for display of stereoscopic video during trickplay includes technology to allow continuous viewing of stereoscopic video even when a stereoscopic video is paused, as in Patent Literature 3.
Technology for overlaying and displaying multiple layers includes technology which, in rendering graphics when a multi-screen display has exceeded a predetermined number of screens, skips frames during the graphics rendering period for at least one or more input images determined to have low priority, as in Patent Literature 4.